Idaho Skies Transcript for November 19th and 20th

RACHEL
Welcome to Idaho Skies for November 19th and 20th. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
On the 20th we celebrate the birthday of American astronomy Edwin Powell Hubble

PAUL
Most listeners will be familiar with the Hubble Space Telescope. The telescope was launched into Earth orbit by the Space Shuttle in 1990 and named after astronomer Edwin Hubble. Early last century, astronomers thought the entire night sky of stars as being the entire universe. Astronomers did not believe that the stars were grouped into units that were larger than star clusters and smaller than the entire universe.

RACHEL
A raging debate between astronomers in 1920 was whether or not the fuzzy oval clouds that they could see through telescopes were large groupings of stars. Those believing that this was the case called them island universes. These island universes, they claimed, were as large as the Milky Way galaxy and millions of lights years away. That there could be millions of island universes in a universe at least hundreds of millions of light years across was too much for some astronomers to accept.   

PAUL
In 1912, astronomer Henrietta Leavitt discovered that some types of variable stars can be used to estimate distances. The stars were called Cepheid variables and Leavitt noticed that the brighter these stars were, the longer it took for them to oscillate in brightness. Hubble used his observations of the great nebula in Andromeda and the relationship Leavitt discovered to determine that the nebula was 1.5 million light years away, or far outside the Milky Way galaxy.

RACHEL
Hubble then used a spectroscope to discover an important fact about these island universes or galaxies. When the light of an external galaxy is split with a spectroscope, the colors emitted by each element are shifted. The amount of shift depends on how fast the galaxy was moving towards or away from the observer. Hubble discovered that the more distant the galaxy, the faster it was receding from us. In other words, the universe of millions of galaxies was expanding. And not only that they were expanding, but that they had originated from a point several billion years ago. 

PAUL
That’s Idaho Skies for the 19th and 20th of November.

RACHEL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Rachel…

PAUL
…and Paul.

RACHEL
Dark skies and bright stars.